1. Field of the Invention
The present invention relates to a surgical device and method. More specifically, it is a device assembly and method adapted to form a circumferential conduction block along a circumferential region of tissue along a posterior left atrial wall and surrounding a pulmonary vein.
2. Description of the Related Art
Many abnormal medical conditions in humans and other mammals have been associated with disease and other aberrations along the walls that define several different body spaces. In order to treat such abnormal wall conditions of the body spaces, medical device technologies adapted for delivering specific forms of ablative energy to specific regions of targeted wall tissue from within the associated body space have been developed and disclosed.
Cardiac arrhythmias, and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. In patients with normal sinus rhythm, the heart, which is comprised of atrial, ventricular, and excitatory conduction tissue, is electrically excited to beat in a synchronous, patterned fashion. In patients with cardiac arrhythmia, abnormal regions of cardiac tissue do not follow the synchronous beating cycle associated with normally conductive tissue in patients with sinus rhythm. Instead, the abnormal regions of cardiac tissue aberrantly conduct to adjacent tissue, thereby disrupting the cardiac cycle into an asynchronous cardiac rhythm. Such abnormal conduction has been previously known to occur at various regions of the heart, such as, for example, in the region of the sino-atrial (SA) node, along the conduction pathways of the atrioventricular (AV) node and the Bundle of His, or in the cardiac muscle tissue forming the walls of the ventricular and atrial cardiac chambers.
Cardiac arrhythmias, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmias may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. These foci may act as either a trigger of paroxysmal atrial fibrillation or may sustain the fibrillation. Recent studies have suggested that focal arrhythmia often originates from a tissue region along the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Percutaneous catheter ablation techniques have been disclosed which use end-electrode catheter designs with the intention of ablating and thereby treating focal arrhythmias in the pulmonary veins. These ablation procedures are typically characterized by the incremental application of electrical energy to the tissue to form focal lesions designed to ablate the focus and thereby interrupt the inappropriate conduction pathways.
One example of a focal ablation method intended to destroy and thereby treat focal arrhythmia originating from a pulmonary vein is disclosed by Haissaguerre, et al. in xe2x80x9cRight And Left Atrial Radiofrequency Catheter Therapy Of Paroxysmal Atrial Fibrillationxe2x80x9d in Journal of Cardiovascular Electrophysiology 7(12), pp. 1132-1144 (1996). Haissaguerre, et al. disclose radiofrequency catheter ablation of drug-refractory paroxysmal atrial fibrillation using linear atrial lesions complemented by focal ablation targeted at arrhythmogenic foci in a screened patient population. The site of the arrhythmogenic foci were generally located just inside the superior pulmonary vein, and were ablated using a standard 4 mm tip single ablation electrode.
In another focal ablation example, Jais et al. in xe2x80x9cA Focal Source Of Atrial Fibrillation Treated By Discrete Radiofrequency Ablationxe2x80x9d Circulation 95:572-576 (1997), applies an ablative technique to patients with paroxysmal arrhythmias originating from a focal source. At the site of arrhythmogenic tissue, in both right and left atria, several pulses of a discrete source of radiofrequency energy were applied in order to eliminate the fibrillatory process.
There is a need, however, for a circumferential ablation device assembly and method adapted to electrically isolate a substantial portion of a posterior left atrial wall from an arrhythmogenic focus along a pulmonary vein. In particular there is still a need for such an assembly and method which provides a circumferential ablation member secured to the distal end of an elongate catheter body and which includes an ablation element adapted to form a circumferential conduction block along a circumferential region of tissue which either includes the arrhythmogenic focus or is between the arrhythmogenic focus and a substantial portion of the posterior left atrium wall.
This invention is a tissue ablation system and method that treats atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. In general, the system includes a circumferential ablation member with an ablation element that ablates the tissue at the location, and also includes a delivery assembly for delivering the ablation member to the location. The circumferential ablation member is generally adjustable between different configurations to allow for in one configuration the delivery through a delivery sheath into the atrium, and in another configuration the ablative coupling between the ablation element and the circumferential region of tissue at the location.
According to one mode of the tissue ablation system, the circumferential ablation member is adjustable to a position wherein a circumferential wall has a distal facing surface that surrounds the longitudinal axis of a cooperating delivery member. The ablation element ablatively couples to a circumferential area that is normal to the distal facing surface. The distal facing surface is configured such that the circumferential area coincides with the circumferential region of tissue when the wall is adjusted to the second position at the location, and therefore the ablatively coupled ablation element is adapted to ablate the circumferential region of tissue there.
According to another mode of the invention, a circumferential ablation member has a circumferential support member that is adjustable between a first position which is adapted to be delivered through a delivery sheath into the atrium and a second position having a substantially circumferentially looped shape. An ablation element is located substantially along the circumferential support member and is adapted to ablatively couple to a circumferential area adjacent to the support member in the second position. The looped shape of the circumferential support member is configured such that the circumferential area coincides with the circumferential region of tissue when the circumferential support member is adjusted to the second position at the location. A positioning assembly that is coupled to the circumferential support member such that the circumferential support member may be adjusted between the first and second positions when the circumferential support member is substantially radially unconfined within the atrium. In addition, a delivery assembly cooperates with the circumferential ablation member and is adapted to at least in-part deliver the circumferential ablation member to the location.
In one aspect of this mode, the circumferential support member has an elongate body that extends distally from a delivery member and is sufficiently straight in the first position to fit within a delivery sheath. The elongate body is reconfigured into the looped shape for ablation when the circumferential support member is adjusted to the second position.
In one variation of the system according to this aspect, the delivery member has a passageway extending between a distal port adjacent the proximal end of the elongate body and a proximal port located along the proximal end portion of the delivery member. The positioning assembly adjusts the position of the ablation member by use of a pull-wire that is moveably engaged within the passageway such that the proximal end portion of the pull-wire extends proximally through the proximal port, and the distal end portion of the pull-wire extends distally through the distal port where the pull-wire is secured to the distal end of the elongate body. In the first position the first and second ends of the elongate body are spaced along the pull-wire with the intermediate region of the elongate body extending along the longitudinal axis adjacent to the pull-wire. The circumferential support member is adjustable to the second position at least in part by adjusting the relative position of the pull-wire with respect to its moveable engagement within the passageway of the delivery member such that the proximal and distal ends of the elongate body are longitudinally collapsed toward each other. Such longitudinal repositioning of the ends of the elongate body cause the intermediate region to deflect radially into the desired looped shape.
According to a further feature of this variation, at least one indicator which indicates when the circumferential ablation member is in the second position, such as in one further variation by use of first and second radiopaque markers on the opposite ends of the elongate body, or by use of visible indicators on the proximal aspects that indicate the relative positioning of the pull-wire versus the delivery member.
In another aspect of this mode, the circumferential support member comprises an elongate body with a distal end secured to the distal end portion of the first delivery member and a proximal end secured to the distal end portion of the second delivery member. The positioning assembly comprises an outer member with a proximal end portion and a distal end portion that surrounds the distal end portions of the first and second delivery members and that has a longitudinal axis. The distal end portion of at least one of the delivery members is moveable along the outer member, such that in the first position the elongate body extends distally from the first delivery member substantially along the longitudinal axis, and in the second position the delivery members are longitudinally adjusted relative to each other and also relative to the outer member such that the elongate body is positioned externally of the distal end portion of the outer member with the elongate body adjusted into the substantially circumferentially looped shape.
According to various of the modes and more particular aspects herein summarized, one further variation provides an anchor along a distal end portion of a delivery member associated with the system and which is adapted to secure the delivery member within the pulmonary vein while the circumferential ablation member is being ablatively coupled to the circumferential region of tissue. In one more detailed example the anchor includes an expandable member which radially expands to engage the pulmonary vein in order to secure the delivery member in place during ablation.
In another aspect of this mode, the positioning assembly includes an array of circumferentially spaced splines that are positioned around the longitudinal axis. Each spline has a proximal end portion coupled to the distal end portion of the delivery member and a distal end portion coupled to the circumferential support member. Each spline is adjustable between a first configuration, wherein the distal end portion of the spline extends substantially along the longitudinal axis, and a second configuration, wherein the distal end portion of the spline extends radially away from the longitudinal axis. The first position for the circumferential support member according to this aspect is characterized at least in part by each of the splines being adjusted to the first configuration. The respective second position is characterized at least in part by each spline being adjusted to the second configuration.
According to one variation of the spline aspect of this mode, each spline provides a single elongate member that terminates distally where it is secured to the circumferential support member. In another variation, each spline provides a looped member having an apex along the distal end portion of the spline and two legs extending proximally from the apex along the proximal end portion of the spline. Further to this latter variation, the circumferential support member is threaded through the apexes of the circumferentially spaced splines. Moreover, according to a further feature at least one of the splines is used to help couple the ablation element to the ablation actuator, such as by allowing an ablation actuating member to extend along the spline to an energy source of the ablation element, and more specifically by providing fluid coupling along a passageway along the spline in the case of a fluid ablation element, or electrical coupling of electrical conductor leads along the spline passageway in the case of an electrical ablation element.
In another spline variations: the ablation element has a plurality of individual ablation elements, each extending along the circumferential support member between two adjacent splines; or, the splines comprises a material having a memory to the second configuration, such as by means of a shape memory material such as a nickel titanium alloy.
Further to other aspects of this mode, the ablation element may be one or more specific types of ablation elements, such as fluid, electrical, cryo, microwave, thermal, light-emitting, or ultrasound ablation elements. element.
In one specific variation incorporating the electrical ablation aspect of this mode, at least one electrode is provided along the circumferential support member which is adapted to be coupled to an electrical current source. A porous wall substantially surrounds the electrode within an enclosed fluid chamber which is adapted to be fluidly coupled to a source of electrically conductive fluid. The porous wall is further adapted to electrically couple an ablative electrical current between the circumferential region of tissue positioned coincident to the circumferential area and the electrode via the electrically conductive fluid.
According to another mode of the invention, a circumferential ablation member includes a housing, a mechanical positioning assembly that adjusts the housing between certain specific first and second conditions, and an ablation element also cooperating with the housing to ablate the circumferential region of tissue. Further to this mode, the housing is mechanically adjustable between a first condition and a second condition. In the first condition the distal wall is substantially radially collapsed such that the housing is adapted to be delivered through a delivery sheath into the atrium. In the second condition the distal wall is radially extended at least in part from the longitudinal axis with a distal orientation and a distal facing surface located along a circumferential region that surrounds the longitudinal axis. A mechanical positioning assembly is coupled to the housing to mechanically adjust the housing between the first and second conditions. An ablation element cooperates with the housing and is adapted to ablatively couple to a circumferential area normal to the distal facing surface along the circumferential region when the housing is in the second position. The distal facing surface is configured such that the circumferential area coincides with the circumferential region of tissue when the housing is adjusted to the second condition at the location, and therefore the ablation element is adapted to ablate the circumferential region of tissue in that position.
In one beneficial aspect of this mode, the distal wall in the second condition comprises a porous membrane that encloses at least in part a fluid chamber within the housing. The distal facing surface is located along the porous membrane, and the porous membrane is adapted to ablatively couple a volume of ablative fluid within the fluid chamber to the circumferential area. In one further regard, the porous membrane is adapted to allow the volume of ablative fluid to flow from within the fluid chamber and into the circumferential area. Still further, the ablation element may comprise a volume of ablative fluid medium within the fluid chamber and that ablatively couples with the circumferential area across the porous membrane. In a still further variation, the porous membrane is constructed at least in part from a porous tetrafluoropolymer. In another variation, the ablation element includes an ablative energy source located within the fluid chamber.
In another more detailed aspect of this mode, the housing has an outer jacket with a distal end portion and a proximal end portion, the distal wall is located along the distal end portion, and a proximal wall is located along the proximal end portion. The mechanical positioning assembly comprises an array of longitudinal splines that are circumferentially spaced around the longitudinal axis, wherein each of the longitudinal splines has a distal end portion and a proximal end portion and an intermediate region therebetween. The distal and proximal end portions of the outer jacket are positioned to surround at least a part of the proximal and distal end portions of the splines, respectively. According to this relationship, in the first condition the proximal and distal end portions of each spline are respectively spaced along the longitudinal axis with the intermediate region being substantially radially collapsed within the outer jacket. The housing is adjusted to the second condition by longitudinally collapsing the relative position of the proximal and distal end portions of each spline such that the intermediate region of each spline and outer jacket adjacent thereto deflects radially outwardly from the longitudinal axis such that distal and proximal orientations, respectively, are given to the distal and proximal walls. In one variation of this aspect, the outer jacket comprises an elastomeric material.
In another aspect of this mode the housing also has a proximal wall which in the second condition has a proximally facing surface. The proximal wall according to this aspect is connected to the distal wall, such as in a still further variation by being formed from an integral member. In a still more detailed variation however, the distal and proximal walls are connected along at least one of (a) an outer circumferential region that circumscribes the circumferential region that includes the distal facing surface, or (b) an inner circumferential region that is circumscribed by the circumferential region that includes the distal facing surface. In yet another variation, the mechanical positioning assembly provides at least one support member extending between the distal and proximal walls at least across an inner circumferential region, which is circumscribed by the circumferential region that includes the distal facing surface, and the circumferential region with that distal facing surface.
According to another aspect of the mechanically adjustable ablative housing mode, the mechanical positioning assembly is coupled to the delivery member.
In another more detailed aspect of this mode, the mechanical positioning assembly comprises an array of splines that are circumferentially spaced around the longitudinal axis of the delivery member. Each spline has a distal end portion coupled to the distally oriented wall and a proximal end portion coupled to the distal end portion of the delivery member. Also, each spline is adjustable between a first position which is substantially radially collapsed and extending along the longitudinal axis and a second position wherein the distal end portion of the spline extends radially outwardly from the longitudinal axis. Accordingly, the first and second positions for the splines characterize at least in part the first and second conditions for the housing.
Further to this aspect, in one variation the ablation element comprises an energy source that is located along a spline at a position corresponding to the circumferential region.
According to another mode of the invention, a circumferential ablation member coupled to the distal end portion of a delivery member includes an array of splines supporting an array of individual ablation elements with each ablation element being supported along a support region of one of the splines. The splines are circumferentially spaced around the longitudinal axis. Each spline is adjustable between a first condition and a second condition, wherein the respectively supported individual ablation element is adjustable between a first radial position and a second radial position. Further to this assembly, each spline is substantially radially collapsed and extends substantially along the longitudinal axis in the first condition such that the circumferential ablation member is adapted to be delivered through a delivery sheath into the atrium. In the second condition, the support region of each spline extends at least in part radially away from the longitudinal axis. Each of the individual ablation elements is thus held by the supporting spline in the second radial position with the array of individual ablation elements being spaced along a circumferential pattern that surrounds the longitudinal axis. This circumferential pattern is specifically configured such that the array of individual ablation elements is adapted to engage and ablate the circumferential region of tissue when the splines are adjusted to the second condition at the location.
In one aspect of this mode, each of the splines has a memory to the second condition, such as by being constructed from a shape-memory material which more specifically may be a nickel-titanium alloy.
In another aspect, an outer member surrounds the distal end portion of the delivery member. The splines are adapted to be moved in and out of the outer member in order to adjust their shape between the first and second positions.
According to additional aspects of this mode, the distal end portion of each of the splines in the second position may have a radius of curvature either away from the longitudinal axis, or in another aspect the radius of curvature may be toward the longitudinal axis.
According to still further aspects of this mode, the ablation element may be one of a number of different types, including one or more of the following: an electrical current ablation element; a thermal ablation element; an ultrasound ablation element; a microwave ablation element; a cryoablation element; a fluid ablation element; or a light emitting ablation element.
In another mode of the invention provides a contact member in combination with a distally oriented ablation element, both being coupled to a delivery member. The contact member is adjustable between a first condition for delivery through a delivery sheath into the atrium and a second condition for circumferential ablation wherein the contact member comprises a circumferential wall that surrounds the longitudinal axis. The ablation element has an ablative energy source that is located along the distal end portion of the delivery member, and cooperates with the contact member such that the ablative energy source emits a circumferential pattern of energy having a distal orientation through the circumferential wall and into a circumferential area normal to the circumferential wall. Electrical current is not ablatively coupled between the ablative energy source and the circumferential area according to this mode. The ablation element and contact member are configured such that the circumferential area coincides with the circumferential region of tissue when the contact member is adjusted to the second condition at the location.
In one aspect of this mode, the contact member is an inflatable balloon and the ablation element cooperates with the circumferential area as described above through the balloon""s outer skin.
According to still further aspects of this mode, the ablation element may be one of a number of different types, including one or more of the following: an electrical current ablation element; a thermal ablation element; an ultrasound ablation element; a microwave ablation element; a cryoablation element; a fluid ablation element; or a light emitting ablation element.
In one variation of the ultrasound ablation element aspect, an ultrasound transducer assembly is mounted onto the distal end portion with a distally oriented face which is adapted to emit an ultrasonic energy signal distally at an angle relative to the longitudinal axis and through the circumferential wall of the contact member. In still a further more detailed variation, the transducer is conically shaped with an outer conical surface having a distal orientation. In another detailed variation the transducer has a curved distal face.
In still a further detailed variation, the ultrasound transducer assembly has at least one ultrasound transducer panel that is adjustable from a radially collapsed position to a radially extended position having a distally oriented face that is adapted to emit the circumferential pattern of energy with the distal orientation. Further to this transducer panel variation, the transducer panel may be adjustable as described by use of an expandable member located between the panel and the distal end portion of the delivery member, which expandable member may be a balloon structure or a cage structure.
Other modes, aspects, variations, and features of the invention shall become apparent to one of ordinary skill upon review of this application, and in particular by reference to the detailed disclosure of the invention which follows below.